Neothiazolocarbocyanine dye and method of preparing it



Patented Mar. 19, 1935 r UNITED STATES 'NEOTHIAZOLOCARBOCYANINE DYE AND METHOD PREPARING IT Leslie G. S. Brooker, RochestenN. Y., assignor to Eastman KodakCompany, Rochester, N. Y., a

, corporation of New York 7N0 Drawing Application June 30, 1931,

' Serial No. 548,025 r 17 Claims. (01'. 2 0-44) This invention relates to a newcompositionoi matter and particularly to anewcla'ssof photographic sensitizing dyes and a method forv their preparation. r

Most ordinary photographic emulsions are comparatively indifferent to those colors of the spec-r trum. of longer wave-length 'and'for. that reason various types of sensitizing eyes have,l'iefen suggestedfor use. These mayll bejincorporatedlin' the emulsion, or employed ifnfa sensitizing bath, in which the photographic filmor plate isbathed. Many cyanine dyes have been ldescrib'ed for this purpose containing the .benzothiaz'olenucleus. Dyes containing the. naphthotliiazole nucleus arev described in my co-pending applications, Serial Nos. 337,177 filed'February 2, 1929, 435,104 filed March 12, 1930, 435,105 filed March 12, 1930, and dyes containing the thiazoline nucleus are described in my co-pending. application Serial No. 460,548 filed June 11, 1 930... T

An object of the present invention is to provide a process'for the preparation of photographic sensitizersof a new type containing the thiazole nucleus. These dyes may be termed neothiazolo-v overcoating', thereby increasing the spectralsem' sitiveness of the emulsion. Other objects will hereinafter appear.

r I The thiazole ,ring isusually numbered in the, a following manner, and this system of numbering is used in the present application; v

il 2 H I .The base 2 methylthiazole, ,or' a substituted 2 methyl-thiazol'e, e. g. 2-methyl 4 phenylthiazole,

may be convertedinto an alkylquaternary salt by heating it with, for instance,.a dialkyl sulfate or an alkyl p-toluenesulfo'nate or an alkyl'iodide. When the alkyl halides are used, quaternary alkyl iodides are produced which on treatment with ethylorthoformate and pyridine undersappropriate conditions yield as a principal product thi-J azolocarbocyanines.

If trialkyl ortho esters of carboryliclacids other than formic acidare employed in the condensation, thiazolocarbocyanines are! obtained with.

substituent groupings attached to the central carbon atom. of the three-carbon carbocyanine chain. For instance triethylorthopropionate yields 7-ethylthiazolocarbocyanines. These dyes are fully dealt with in my co-pending application Serial No. 619,962 filed June 29, 1932..

The 2-methyl thiazoles also yield such dyes as thiazoloiso-cyanines and thiazolo-ip-cyanines. These are ,dealt with in my co-pending application Serial No. 619,960'fi1ed June 29, 1932.

In the present case, dialkylsulfates and more especially. alkyl p-toluenesulfonates are used for the preparation of the thiazole alkylquaternary salts, and these when treated with an excess of ethyl orthoformate in anhydrous pyridine yield the neothiazolocarboeyanines of the instant application preponderating amounts. amount ofsirhple' thiazolocarbocyanine frequently accompanies the neothiazolocarbocyanine, but as a rule the latter dyes are less soluble than these simple thiazolocarbocyanines and can readily be isolated ina pure state.

Analytical results indicate that the molecule of neothiazolocarbocyanine contains three thiazole nuclei, in two of whichthe nitrogen atoms" are in the pentavalent state. The dye is probably representedby one of the following formulae:-

In these formulae A and B represents univalent atoms or groupings such as hydrogen, alkyl or aryl; R stands for .alkyl and X represents a suitable acid radical such, for example, as the halides, p-toluene sulfonate, alkylo sulfate or in fact any suitable acid radical which will not greatly decrease or destroy the sensitizing properties of the dye,this radical being necessary. to give electrical neutrality to the molecule. In the claims the phrasea suitable acid radicalis employed to designate this group of acid radicals.

In Formula I, one molecule of ethylorthoformate is supposed to have reacted with three molecules of quaternary salt, whilst Formula II may be arrived at by supposing that two mole- A small cules of ethylorthoformate react with three molecules of the alkyl quaternary salt. For various reasons, it is thought that Formula II is the more probable one, and the analytical evidence favors it in most cases. invention is not affected by theoretical considerations relating to the exact structure of the mole- PREPARATION OF NEO'IHIAZOLOCARBOCYANINEVS Step I The thiazole base containing a reactive methyl group is first converted into an appropriate alkyl quaternary salt, by heating with, for instance, an alkyl sulfonic ester, such as an alkyl p-toluene sulfonate. The dialkyl sulfates may also be employed, but the yields are usually lower.

A and B are hydrogen atoms or substituent. atoms or groups, R stands for alkyl and X stands for a suitable acidic radical such as p toluene sulfonate (O.SO2.C7H7) or alkyl sulfate (O.SOz.OR)

Step II The thiazole alkyl quaternary salt is heated in anhydrous pyridine with ethyl orthoformate (conveniently employed in excess) and dye formation occurs. This is most probably represented as follows: A

(In the above formulae, Et represents the ethyl group C2H5). The dye may be isolated at this stage or it may be isolated as a more sparingly soluble salt in Step III.

In any event, the utility of my siderable excess.

Step III, I This is a simple step and consists of double decomposition. The reaction mixture, conoen- A.

trated or otherwise, or the solution of the dye in some other solvent-is treated withan aqueous solution of an alkali salt of the acid whose anion it is desired to introduce into the dye. For instance, the p-toluene sulfonate of a dye may be treated with an aqueous solution of potassium iodide orsodium iodide or ammonium bromide; This alkali salt is conveniently employed in con- The dye iodides, for example, are usually fairly insoluble in cold aqueous solutions' containing excess of inorganic iodide, and

may therefore be conveniently obtainedby filtrationin the usual way.

Step IV 'The crude dyesare finally purified, and'this' involves separation from the normal 'thiazolocarbocyanines which areusually. formed simuljtaneously. In most; cases'theseimpurities'are more soluble tharrfthe neothiazolocarbOcyanihes; but not invariably so; When the solubility rela tionship of the two dyes is established; separation may be effectedusing'the methods of trantional crystallization; i

The foregoing steps are illustrated in the lowing examples in'whioh thedyes produced are named in accordance with'my preferredgeneral,

Iodide 'of the neothiaiolocarbocyaninegfrorrr 2-methy1thiazole metho-p-toluenesulfonate 3,3 dimethyl ILB-(thiazyl 2 methiodide) v in y'l] thiazolocarbocyanine iodide.

9.9 g. Z-methylthiazole (3 mols.) was heated with 18.6 g. methyl p-toluenesulfonate (3 mols.) on the steam bath. Addition'took' place. rapidly. and solidification appeared to, be complete 'in about five minutes. The solid quaternar'y'salt was dissolved in 150 cc. boiling dry pyridine and;

16.5 cc. ethyl orthoformate (3' mols. 50%.exce'ss)f added and the wholerefluxed 'for'flve hours. [On I standing in the cold, crystals of the neothiazolo carbocyanine nretho-p-toluenesulfonate 'sepa' rated. These were filtered on" and washed with.

cold pyridine and then dissolved in boili'ng methyl alcohol and an aqueous solution of 'excessjof potassium iodide in warm distilledwater added and the mixture stood aside-to crystallize out. 7

The iodide of the dye so produced was filtered off and washed and the more soluble neothiazolo-zv carbocyanine was removed bytreatment with a hot mixture of acetone and methyl alcohol. The

dye was purified by crystallization "from methyl 7 alcohol and was finally obtained as a sun purplish-black felted crystalline mass and gave. 60;

a violet solution in methyl alcohol.

Example II Iodide of the neothiazolocarbocyanine from.

2-methylthiazole etho-p-toluenesulfonate 3-,3'idiethyl-7-[p-(thiazyl-2 'ethiodide)-vinyllthiazolocarbocyanine iodide. H 9.9 g. 2-methylthiazole. (3 'mols.) wa'sheated' with 20 g. ethyl p-toluenesulfonate (3 mols.) on Thecrude etho-p-toluenesulfonate was: boiled under reflux with 40 ee. anhydrous pyridine and 22.2 cc. ethyl orthoformate (4 mols.; Most of the solvent;

an oil bath at 117-120 C. overnight. 2-methylthiazole excess) for five hours. was removed by concentration in vacuo and the;

residue was stirred with hotidistilledwater and.

anexcess of potassium iodide was added and the whole well mixed and stood aside to crystallize out. The dye was then filtered and washed. The residue was then dried and consisted of greenish-bronze crystals apparently mixed with darker dull green crystals. The dye was boiled with acetone and filtered hot but the filtrate was quite bluish and little or no crimsonthiazolocarbocyanine seemed to-bepresent inv the preparation. The dye was'crystallized from methyl alcohol and gave beautiful greenish-bronze plates which imparted a violetcoloration to methyl alcohol. I

Example III Iodide of the neothiazolocarbocyanine from 2,4-dirnethy1-thiazole metho-p-toluenesulfonate 3 4,3',4' tetramethyl 7E5 (4 methylthiazyl -2 methiodide) vinyl] -thiazolocarbocyanine iodide.

11.3 g. 2,4-dimethy1thiazole (3 mols.) was heated on an oil bath at 115 C. with 18.6. g. methyl p-toluenesulfonate (3 mols.) for about an hour, solidification occurring within the first five rninutes or less. The quaternary salt so obtained was refluxed for 4 hours with pyridine (60 cc.) and 22.2 cc.- ethyl orthoformate (4 mols.). During the reaction much solid separated. The reaction mixture was allowed to cool overnight and the p -toluenesulfonate of the dye was then filtered oil. The dye was converted into the iodide by boiling it withmethyl alcohol and slowly stirring in a hot solution of potassium iodide in water. The whole was allowed to cool, and was then filtered and the dye washed. When dried, the iodide of the dye consisted of a Example IV V Iodide oi the neothiazolocarbocyanine from 2,4 dimethyl thiazole methiodide) -vinyll -thiazolocarbocyanine iodide. 12.6 g. dimethylsulfate (3 mols.)- was placed in i a flask provided with a reflux condenser and 11.3

g. 2,4-dimethylthiazole (3 mols.) added in small portions down the condenser. This addition was accompanied by much heat evolution. The prodnot was heated for a further hour at about 115 C. The crude quaternary salt was refluxed for 4 /2 hours with 60 00. pyridine and 222cc. ethyl orthoformate i mols.). At first two layers formed but these gradually merged during the course of the reaction. After standing for two days, solid separated in the reaction 'mixture. This was the methylsulfate of the dye and it was filtered off, washed, and dissolved in boiling methyl alcohol and the dye-precipitated as the iodide by adding an excess of potassium iodide in hotdistilled water. The dye was filtered off when cold andwashed. The air-dried dye consisted of a greenish-grey powder. The crude dye contained the normal thiazolocarbocyanine, and this was mostly removed by boiling with methyl alcohol and filtering hot. The dye was then recrystallized from more methyl alcohol and consisted of a felted mass of dark greenish-brown needles which imparted a violet-blue coloration to the solvent.

metho methylsulfate 3,4,3',4 tetramethyl 7H9 (4 methylthiazyl 2.

Example V V I Iodide of the j neothiazolocarbocyanine from 2,4 dimethyl-thiazole etho-p toluenesulfonate 7 4A- diphenyl-3,3 diethyl-7 [c- (4-methylthiazy1- 2 ethiodide)-vinyl]-thiazolocarbocyanine iodide. 11.3 g. 2,4-dimethylthiazole (3 mols.) was heat-' ed overnight at 115-120? C. with 20 g. ethyl ptoluenesulfonate (3 mols.). The crude quaternary salt, which Was a light brown viscous liquid,

was refluxed for 5 hours with 40 cc. pyridine and 22.2 cc. ethyl orthoiormate (4 mols.). The re-- action mixture was concentrated in vacuo and the residue mixedwith hot distilled water and an excess of potassium iodide added. The dye was allowed to crystallize out and was then filtered off and washed. Theair-dried dye consisted of larly a fourth and fifth crop. These crops consisted of tolerably pure neothiaz'olocarbocyanine. The dye was crystallized from methyl alcohol into beautiful greenish needles which became dull on drying and which gave aviolet-blue solution in methyl alcohol.

Example VI Iodide of the neothiazolocarbocyanine from 2- methyl-4rphenylthiazole metho-p-toluenesulfonate 4,4- diphenyl-3,3' dimethyl-7 [fi- (l-phenylthiazyl -2 methiodide) vinyl] -th iazolo carbocyanine iodide.

8.8 g. of 2-methyl-4-phenylthiazole (3 mols.) was heated with 9.3 methyl p-toluenesulfonate (3 mols.) for forty hours at l125"- C. The product, a viscous liquid, was refluxed for five hours with pyridine cc.) and 11 cc. ethyl or thoformate (4 mols.) The dye was precipitated as a tar by adding an excess of potassium iodide dissolved in hot water. After standing tocool, and pouring off the aqueous liquor, the dye was stirred with some boiling acetone when it became crystalline and wascooled and filtered. The airdried dye consisted of, a purplish-brown crystalline powder. The crimson normal thiazolocarbocyanine was removed by boiling with a mixture or methyl alcohol'an'd acetone. The dye was then recrystallized from methyl alcohol and when dried consisted of a dull greenish-brown powder. The color of the methyl alcoholic solution was blue. 7 r 1 Example VII Iodide of the neothiazolocarbocyanine from 2 methyl-4-phenylthiazo1e ethO-p-tohiensulfonate 4,4- diphenyl 3,3 diethy1-7 [c- (4 phenylthiazyl- Z-ethiodide) vinyl] -thiazolocarbocyanine iodide.

8.8 g. ,of 2 methyle-phenylthiazole (3 mols.)-

' type of 7-substituted thiazolocarbocyanine.

solution of an excess of potassium iodide in water and stood aside to cool. The dye was filtered off and as it was somewhat tarry it was boiled was acetone, cooled, and filtered. The dye when dried consisted of a dull bronze colored powder. The dye was boiled with a mixture of methyl alcohol and acetone and filtered hot, but thesolution was quite blue, as though little or no normal thiazolocarbocyanine were present. The dye was finally crystallized-from methyl alcohol and consisted of small coppery crystals which gave a blue solution in the solvent.

As previously indicated and from the foregoing examples it will be observed that the neothiazolocarbocyanines are produced by the condensation of thiazole alkyl quaternary salts, containing reactive methyl groups (Z-methylthiazole alkyl quaternary salts) with ethyl orthoformate in some suitable solvent such as anhydrous pyridine. Analytical evidence suggeststhat 3 molecules of the quaternary salt condense together with one, or more probably two, molecules of ethyl orthroformate. However, not every salt will give suitable yields of the neothiazolocarbocyanines inasmuch assome, notably the iodides, give principally the normal thiazolocarbocyanines in most cases.

-The dyes may also be described as a particular In this case the substituent is an alkylquaternary thiazyl vinyl group. Vinyl is CH2=CH and if one H of the CH2=group is replaced by an alkyl quaternary thiazyl group linked through its 2 position we get the substituent grouping probably present in the neothiazolocarbocyanines.

What I claim as new and desire to secure by Letters Patent is:

1. A neothiazolocarbocyanine salt containing three thiazole nuclei and. having the following structure etln'odide) anine salt, the aryl groups being of the benzene series.

thiazyl-Z methyl quaternary salt) vinyl] -thiazolocarbocyanine salt. 5 I v 9. A 4,4-diphenyl-3,3'diethyl-7[B(4-phenylthiazyl-2 ethyl quaternary salt) vinyl]-thiazolo-' carbocyanine salt. 7

10. A process for the preparation of carbocy anine dyes which comprises condensing, under the influence of heat, three molecular proportions.

of a thiazole alkyl quaternary salt with not more than two molecular proportions of ethyl ortho-' formate in the presence of an organic base which is a solvent for thereactants and which 'acts to bind acid eliminated from the quaternary salt as a result of the condensation.

12. A process for the preparation of carbo cyanine dyes which comprises condensing, under the influence of heat, three molecular proportions of a thiazole alkyl quaternary salt with ethyl .orthoformate in the presence of pyridine.

13. A process for the preparation of carbo cyanine dyes which comprises condensing, under the influence of heat, three molecular proportions of a thiazole alkyl quaternary salt with not more than two molecular proportions of ethyl orthoformate in the presence of pyridine.

'14. A process'for the preparation of carbo cyanine dyes which comprises condensing three molecular proportions of a thiazole dialkyl sulfate with ethyl orthoformate in the presence of an" organic base which is a solvent for the reactants and which acts to bind acid eliminated from the quaternary salt as a result of the condensation.

15. A process for the preparation of carbocyanine dyes which comprises condensing three molecularproportions of a thiazole dialkyl soltions of ethyl orthoformate in the presence of an organic base which is a solvent for the reactants and which acts to bind acid eliminated from the,

quaternary salt as a result of the condensation.

16.A process for the preparation of carbo-' cyanine dyes which comprises condensing three molecular proportions of a thiazole alkyl para 'toluenesulfonate with ethyl orthoformate injthe' presence of an organic base which is a solvent for the reactants and which acts to bind acid as a result eliminated from the quaternary salt of the condensation. I I

17. -A process for the preparation of carboe cyanine dyes-which comprises condensing three molecular proportions of a thiazole alkyl paratoluenesulfonate with not more than two molecular proportions of ethyl orthoformate-in the presence of an organic base which is a solvent for the reactants and which acts to bind acid eliminated from the quaternary salt as aresult of the con-f densation. V LESLIE G. S. BROOKER.

. fate with not .more than two molecular propor- 7' Certificate of Correction Patent No. 1,994,562. March 19, 1935.

LESLIE G. S. BROOKER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, after line 56; insert the following paragraphs:

The general name for I is 3,3-dialkyl-7-(thiazyl-2 alkyl salt) methyl-thiazolocarbocyanine salt and that for II is 3,3-dialkyl-7-[B (thiazyl-2 alkyl salt) vinyl]- thiazolocarbocyanine salt. In these two general names consideration of atoms or groups A and B is omitted for the sake of simplicity. Since these new dyes are believed to be structurally related to the known dye neocyanine, it is logical to call them neothiazolocarbocyanines which has been done herein.

The quaternary alkyl thiazyl group which is linked through the vinylene chain in the above formulae, has the alkyl group and the acidic radical both linked to the nitrogen atom of the thiazyl nucleus. This nitrogen atom is numbered 3 but since it is the only position in this thiazyl nucleus for such linkage, the number need not appear in the name of the dye; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 30th day of April, A. D. 1935.

[SEAL] LESLIE FRLAZER,

' Acting Commissioner of Patents. 

